The 3rd Generation Partnership Project (3GPP) is responsible for the standardization of the UMTS (Universal Mobile Telecommunication Service) system, and LTE (Long term Evolution) is now under discussion as a next generation mobile communication system of the UMTS system. LTE is a technology for realizing high-speed packet-based communication that can reach data rates of more than 100 Mbps on the downlink and of more than 50 Mbps on the uplink. The 3GPP work on LTE is also referred to as Evolved Universal Terrestrial Access Network (E-UTRAN).
Generally, one or more cells are allocated to a radio base station, known in the 3GPP LTE system as eNB (enhanced/evolved NodeB) or eNodeB. In addition, eNodeBs in LTE will interact directly with the core network and with other eNodeBs. A plurality of user equipments can be placed in a cell served by an eNB. A user equipment (UE) can be represented by a mobile phone, a wireless terminal, a laptop, a personal computer, a personal digital assistant, a voice over internet protocol (VoIP) capable phone or any other 3GPP LTE capable UE. A wireless transmission from a UE to a eNodeB is known as a uplink transmission whereas a wireless transmission from the eNodeB to the UE is known as a downlink transmission.
In LTE, the downlink supports channel dependent scheduling in both the time and the frequency domains. For this purpose, the eNodeB is configured to transmit reference signals to a UE. The UE uses the reference signals to determine/estimate the quality of the downlink channel and reports, over the uplink, a channel feedback information report back to the eNodeB. A CSI (channel status information) or a CQI (channel quality indication) are examples of the channel feedback information. Based on the reported information, the eNodeB can schedule resources for the UE and/or adapt the link quality by e.g. changing the modulation scheme or the coding scheme or the transmit power etc.
In 3GPP it has been agreed that, for LTE, the transmission of the channel feedback information can be performed periodically on a so called physical uplink control channel (PUCCH) or a-periodically on a so-called physical uplink shared channel (PUSCH) used for transmitting data.
Thus as described above, in LTE, channel feedback information is transmitted by the UE over the uplink at periodic interval or a-periodic intervals. The UE may also transmit scheduling requests over the uplink in order to request resources. It should be noted that in LTE, the uplink access is controlled by the eNodeB through uplink grants transmitted in the downlink. The UE may inform the eNodeB that data is pending for transmission to the eNodeB.
In the 3GPP technical specifications 3GPP TS 36.321, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification” Two functions are currently standardized buffer status reports and scheduling requests. The buffer status report is used by the UE to indicate to the eNodeB about an amount of data available in a buffer of a UE that is ready for transmission to the eNodeB. A scheduling request message can be expressed with a single bit (one bit) of information, and the UE requests transmission resource allocation for buffer status report using the on-bit information.
When e.g. new data arrives in the UE buffer, a buffer status report is triggered and if the UE does not have an uplink grant allocated for transmitting data, the UE sends a scheduling request message at the next SR opportunity. The eNodeB can assign a UE dedicated periodic SR resources on the PUCCH for sending a scheduling request message. If the UE has been assigned Dedicated SR (D-SR) resources the UE will wait for the next D-SR resource for sending the scheduling request. If the UE does not have D-SR resources allocated on PUCCH the UE performs a Random access SR (R-SR) on the Random Access Channel (RACH) opportunity. If this UE in the time interval for scheduling request also is scheduled an allocation for a channel feedback information report, a collision may occur between the channel feedback information report and the scheduling request message.
A known solution to the collision problem is described in the 3GPP technical specifications 3GPP TS 36.213, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA) Physical layer procedures (Release 8)”. According to this prior art, in case of a collision between the channel feedback information and the scheduling request, the channel feedback information is dropped. This is illustrated in FIG. 1. As shown, a scheduled channel feedback information, here denoted CSI, is dropped due to that it coincides with a resource for a scheduling request, denoted SR. In this exemplary scenario, the SR is assumed transmitted periodically on the PUCCH whereas the scheduled CSI is assumed transmitted a-periodically on the PUSCH. The dashed line illustrates that data arrives in the buffer of the UE.
A drawback with the solution of this prior art is that it leads to a waste of uplink radio resources since the scheduled CSI resource from the UE is dropped. Furthermore, dropping the channel feedback information leads to a waste of uplink grants when a transmission of a channel feedback information is scheduled on the PUSCH. If on the other hand the scheduling request is dropped instead of the channel feedback information, an increased uplink data transmission delay is introduced since the UE has to wait a longer time before being able to send data in its buffer.